Communication systems are known to comprise a plurality of communication units, a limited number of communication resources that are transceived via a predetermined number of repeaters, and a communication resource allocator that allocates the limited number of communication resources among the plurality of communication units. It is also known that communication units may roam from one communication system to another communication system and operate therein. When a communication unit roams into a new communication system, it transmits a registration packet to the communication resource allocator of the new system. Once the communication resource allocator processes the registration packet, it informs the communication unit whether it can register with the communication system or not. If the communication resource allocator allows the communication unit to register with the system, it allocates the communication unit at least one system resource. A system resource may be a temporary unit identification code, a talk group affiliation code, telephone access code or any other service that that communication system is capable of performing.
A difficulty arises when a communication unit that has been temporarily assigned system resources leaves the communication system. A communication unit may leave the communication system either by roaming out of range of the communication system or turning its power off. Under these conditions, the system resources that have been allocated to that communication unit remain assigned to that communication unit even though it is no longer active within the communication system. Thus, preventing other communication units from utilizing these system resources.
Therefore, a need exists for a method that will allow the communication resource allocator to reclaim system resources from inactive communication units.